Evolution of cross-neutralizing antibodies and mapping epitope specificity in plasma of chronic HIV-1-infected antiretroviral therapy-naïve children from India

• Published in: Journal of general virology 2017-07, Vol.98 (7), p.1879-1891
• Main Authors: Makhdoomi, Muzamil A, Khan, Lubina, Kumar, Sanjeev, Aggarwal, Heena, Singh, Ravinder, Lodha, Rakesh, Singla, Mohit, Das, Bimal K, Kabra, Sushil K, Luthra, Kalpana
• Format: Article
• Language: English
• Subjects: Adolescent; Antibodies, Neutralizing - blood; Antibodies, Neutralizing - immunology; Antibodies, Viral - blood; Antibodies, Viral - immunology; CD4 Lymphocyte Count; Child; Child, Preschool; Cross Protection - immunology; Epitope Mapping; Epitopes - immunology; Female; HIV Antibodies - blood; HIV Antibodies - immunology; HIV Envelope Protein gp120 - immunology; HIV Infections - immunology; HIV Infections - virology; HIV-1 - classification; HIV-1 - immunology; Humans; Immunoglobulin G - blood; Immunoglobulin G - immunology; India; Longitudinal Studies; Male; Peptide Fragments - immunology
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/jgv.0.000824

Delineating the factors leading to the development of broadly neutralizing antibodies (bnAbs) during natural HIV-1 infection and dissecting their epitope specificities generates useful information for vaccine design. This is the first longitudinal study to assess the plasma-neutralizing antibody response and neutralizing determinants in HIV-1-infected children from India. We enrolled 26 and followed up 20 antiretroviral therapy (ART)-naïve, asymptomatic, chronic HIV-1-infected children. Five (19.2 %) baseline and 10 (50 %) follow-up plasma samples neutralized ≥50 % of subtypes A, B and C tier 2 viruses at an ID50 titre ≥150. A modest improvement in neutralization breadth and potency was observed with time. At baseline, subtype C-specific neutralization predominated (P=0.026); interestingly, follow-up samples exhibited cross-neutralizing activity. Epitope mapping revealed V3C reactive antibodies with significantly increased Max50 binding titres in follow-up samples from five infected children; patient #4's plasma antibodies exhibited V3-directed neutralization. A salient observation was the presence of CD4 binding site (CD4bs)-specific NAbs in patient #18 that improved with time (1.76-fold). The RSC3 wild-type (RSC3WT) protein-depleted plasma eluate of patient #18 demonstrated a more than 50% ID50 decrease in neutralization capacity against five HIV-1 pseudoviruses. Further, the presence of CD4bs-neutralizing determinants in patient #18's plasma was confirmed by the neutralizing activity demonstrated by the CD4bs-directed IgG fraction purified from this plasma, and competition with sCD4 against JRFLgp120, identifying this paediatric donor as a potential candidate for the isolation of CD4bs-directed bnAbs. Overall, we observed a relative increase in plasma-neutralizing activity with time in HIV-1-infected children, which suggests that the bnAbs evolve.